This invention relates to materials handling equipment, especially methods and apparatus by means of which objects disposed on a pallet can be withdrawn automatically, and more particularly to a method and apparatus for detecting the number of rows of objects in the top layer of a load of objects disposed in a plurality of rows over at least one layer. The invention further relates to a depalletizing method and a depalletizer incorporating the afore-mentioned detecting method and apparatus.
By means of a depalletizer disclosed in U.S. Pat. No. 4,993,915, an entire row of objects can be withdrawn automatically and simultaneously from the top layer of a load disposed on a pallet, either with the aid of the claws described in that patent or with the aid of those described in U.S. Pat. No. 5,169,284. The disclosures of U.S. Pat. Nos. 4,993,915 and 5,169,284 are incorporated herein by reference. Although the apparatus disclosed in these patents operates quite satisfactorily, its use is limited in that the top layer must be complete, i.e., all the rows of objects must be present, in order for the depalletizer to be able to start working completely automatically on a new pallet. Thus, the method of controlling this apparatus is such that when a new pallet is inserted in the machine, the grasping claws automatically move toward the first row of objects in the top layer. Now, it may happen that the top layer is incomplete when the depalletizer is supposed to start its cycle, either because one or more rows are missing when the pallet is inserted in the machine, or because the depalletizing cycle has been interrupted by a machine shutdown when a number of rows of objects have already been transferred, and the seizing cycle must be restarted. Until now, an operator has had to indicate manually the ordinal number of the first row to be seized. This procedure is a drawback to the extent that not only must there be an attentive operator present, but an erroneous indication may lead to the performance of one or more void cycles, hence a reduction in productivity of the machine, or to the damaging of one or more of the objects and/or of part of the depalletizer if a row present in the layer has been reported as lacking.
It is therefore an object of this invention to provide a method and apparatus making it possible to detect the configuration of the uppermost layer of a load disposed in layers and rows on a pallet in order to be able to bring grasping means into a position for withdrawing objects from the top layer.
Another object of the invention is to provide such a method and apparatus by means of which it is possible to detect automatically, without the intervention of an operator, which is the first row of objects to be seized at the beginning of a depalletizing cycle.
Still another object is to provide such a method and apparatus designed to be used on an existing depalletizer without any major modification of the means installed on that machine, and using these already existing means to the maximum.
A further object of this invention is to provide apparatus capable of detecting whether the top layer is horizontal and plane.